Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756522Ab0FQLkF (ORCPT ); Thu, 17 Jun 2010 07:40:05 -0400 Received: from lon1-post-1.mail.demon.net ([195.173.77.148]:61638 "EHLO lon1-post-1.mail.demon.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751976Ab0FQLkC (ORCPT ); Thu, 17 Jun 2010 07:40:02 -0400 Subject: Re: [RFC PATCH] mm: let the bdi_writeout fraction respond more quickly From: Richard Kennedy To: Peter Zijlstra Cc: Jens Axboe , Andrew Morton , Wu Fengguang , lkml , linux-mm In-Reply-To: <1276714466.1745.625.camel@laptop> References: <1276523894.1980.85.camel@castor.rsk> <1276526681.1980.89.camel@castor.rsk> <1276714466.1745.625.camel@laptop> Content-Type: text/plain; charset="UTF-8" Date: Thu, 17 Jun 2010 12:39:56 +0100 Message-ID: <1276774796.1978.11.camel@castor.rsk> Mime-Version: 1.0 X-Mailer: Evolution 2.30.1.2 (2.30.1.2-8.fc13) Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1465 Lines: 39 On Wed, 2010-06-16 at 20:54 +0200, Peter Zijlstra wrote: > On Mon, 2010-06-14 at 15:44 +0100, Richard Kennedy wrote: > > > diff --git a/mm/page-writeback.c b/mm/page-writeback.c > > > index 2fdda90..315dd04 100644 > > > --- a/mm/page-writeback.c > > > +++ b/mm/page-writeback.c > > > @@ -144,7 +144,7 @@ static int calc_period_shift(void) > > > else > > > dirty_total = (vm_dirty_ratio * determine_dirtyable_memory()) / > > > 100; > > > - return 2 + ilog2(dirty_total - 1); > > > + return ilog2(dirty_total - 1) - 4; > > > } > > IIRC I suggested similar things in the past and all we needed to do was > find people doing the measurements on different bits of hardware or so.. > > I don't have any problems with the approach, all we need to make sure is > that we never return 0 or a negative number (possibly ensure a minimum > positive shift value). Yep that sounds reasonable. would minimum shift of 4 be ok ? something like max ( (ilog2(dirty_total - 1)- 4) , 4); Unfortunately volunteers don't seem to be leaping out of the woodwork, maybe Andrew could be persuaded to try this in his tree for a while and see if any one squeaks ? regards Richard -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/